The well typically serves drinking water to portions of North Hollywood in the San Fernando Valley.

The well was shut down in early 2007 after a standard-monthly test of its waters revealed chromium contamination of 200 parts per billion, or four times California's drinking water standards, said Rachel Loftin, the site's project manager for the EPA. The water tainted with chromium, a carcinogen, was never served to the public, she said.

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The state and federal government have worked for decades to clean up groundwater contaminated with volatile organic compounds left as a result of aerospace manufacturing and other industry work in the San Fernando Valley during the 1940s and '50s. At that time, there was little environmental oversight and many companies dumped chemicals on the ground or into storm drains, Loftin said.

"Once it goes to the ground, it's kind of like a coffee press, it leaches through ... and ends up in the groundwater," she said. Chromium, which is often used in metal alloys, also occurs naturally in soil and had been found in that well at lower levels that were acceptable by state drinking water standards before -- but never this high, Loftin said. The well is one of seven that make up the groundwater treatment centers in the North Hollywood region and all the others remain open, according to Loftin.

Honeywell, whose legacy companies Bendix and Allied Signal conducted aerospace industry operations in the area, was ordered by the L.A. Regional Water Quality Control Board to install the additional treatment system.

Officials believe heavy rains released chromium that had been bound up in soil, which then washed its way into the well.

There are two other groundwater Superfund sites in the San Fernando Valley -- federally designated areas that are declared the most severe for toxic contamination in the country, Loftin said. She said construction to clean up this well will take about four to six weeks, and it should be back up and running by the end of summer.

-- Tami Abdollah

Photo: A water utility operator walks past a well near a San Fernando Valley treatment plant. Credit: George Wilhelm / Los Angeles Times